1. Field of the Invention
The present invention relates to a drive transmitting device for transmitting a drive force of a rotational drive member, and an image forming apparatus provided with the same.
2. Description of the Related Art
In image forming apparatuses such as a copying machine, a printer, a facsimile machine, and the like, various rotational members are used. For rotation of the rotational members, it is necessary that a drive force is transmitted from a drive power source such as a driving motor to each of the rotational members. Therefore, a multi-step gear or a timing belt is provided from a gear connected to a drive motor rotating at a high speed for obtaining a great speed reduction ratio, so that the rotational speed is reduced before a drive force is transmitted to the rotational members.
Further, other than a case where a stepping motor or the like is used to control the rotational speed of each rotational member to be reduced with few steps, usually, a gear arrangement is branched from a single drive motor, and an electromagnetic clutch or the like is provided on a rotational shaft or a driving shaft of the rotational member provided at an end, so that a control of switching ON/OFF of the rotation of the rotational member is performed.
As the rotational shaft, generally, a rotational shaft is used which is provided at its one end with a cut-off surface having a D-shaped cross section formed by milling or the like. The cut-off surface on one end of the rotational shaft is engaged with, for example, a flat surface of a D-shaped hole formed in a gear for transmitting a drive force of the electromagnetic clutch, and the other end is engaged with a flat surface of a D-shaped hole formed in the drive input gear of the rotational member, so that a drive force is transmitted from the electromagnetic clutch to the rotational member.
Conventionally, there have been proposed technologies for preventing rattling and wearing which occurs between such rotational shaft and a member to which the rotational shaft is inserted. For example, Japanese Patent Unexamined Publication No. H10-196671 discloses a technology of tightly securing a rotational shaft and a gear (drive-inputting gear) to improve a rotational accuracy of the gear. Here, a slit is formed along an axial direction, and a bush (spacer) having a tapered cylindrical portion is used. An inner circumferential surface of the gear is tapered, and the cylindrical portion of the bush is pressed into a space between the inner circumferential surface of the gear and the outer peripheral surface of the rotational shaft, so that the tight securing is realized. Further, Japanese Patent Unexamined Publication No. 2005-134670 discloses a technology of integrally providing a rotational slide collar (spacer) to opposite ends of a rotational shaft of a conveying stick provided with a rotational wing and made of resin so as to prevent entering of toners into the slide surface with respect to the bearing.
However, according to those conventional technologies, a spacer which covers an outer peripheral surface of a rotational shaft formed to have a cylindrical shape is inserted to a space between an outer peripheral surface of a rotational shaft and an inner circumferential surface of a gear or bearing. In other words, the conventional technologies do not disclose at all about a method for suppressing wearing which occurs between a rotational shaft having a D-shaped cross section and an inner circumferential surface of the bearing.